The present invention relates to a system for decontaminating water and generating water vapor. More particularly, the present invention relates to an improved method that utilizes a series of sensors and a control system to vaporize water, remove dissolved solids and maximize recovery of potable water from contaminated water via a horizontal water processing vessel.
Desalinization (also desalination or desalinisation) refers to one of many processes for removing excess salt, minerals and other natural or unnatural contaminants from water. Historically, desalinization converted sea water into drinking water onboard ships. Modern desalinization processes are still used on ships and submarines to ensure a constant drinking water supply for the crew. But, desalinization is increasingly being used in arid regions having scarce fresh water resources. In these regions, salt water from the ocean is desalinated to fresh water suitable for consumption (i.e. potable) or for irrigation. The highly concentrated waste product from the desalinization process is commonly referred to as brine, with salt (NaCl) being a typical major by-product. Most modern interest in desalinization focuses on developing cost-effective processes for providing fresh water for use in arid regions where fresh water availability is limited.
Large-scale desalinization is typically costly and generally requires large amounts of energy and an expensive infrastructure. For example, the world's largest desalinization plant primarily uses multi-stage flash distillation and can produce 300 million cubic meters (m3) of water per year. The largest desalinization plant in the United States desalinates 25 million gallons (95,000 m3) of water per day. Worldwide, approximately 13,000 desalinization plants produce more than 12 billion gallons (45 million m3) of water per day. Thus, there is a constant need in the art for improving desalinization methods, namely lowering costs and improving efficiency of the related systems.
Desalinization may be performed by many different processes. For example, several processes use simple evaporation-based desalinization methods such as multiple-effect evaporation (MED or simply ME), vapor-compression evaporation (VC) and evaporation-condensation. In general, evaporation-condensation is a natural desalinization process performed by nature during the hydrologic cycle. In the hydrologic cycle, water evaporates into the atmosphere from sources such as lakes, oceans and streams. Evaporated water then contacts cooler air and forms dew or rain. The resultant water is generally free from impurities. The hydrologic process can be replicated artificially using a series of evaporation-condensation processes. In basic operation, salt water is heated to evaporation. Salt and other impurities dissolve out from the water and are left behind during the evaporation stage. The evaporated water is later condensed, collected and stored as fresh water. Over the years, the evaporation-condensation system has been greatly improved, especially with the advent of more efficient technology facilitating the process. But, these systems still require significant energy input to evaporate the water. An alternative evaporation-based desalinization method includes multi-stage flash distillation, as briefly described above. Multi-stage flash distillation uses vacuum distillation. Vacuum distillation is a process of boiling water at less than atmospheric pressure by creating a vacuum within the evaporation chamber. Hence, vacuum distillation operates at a much lower temperature than MED or VC and therefore requires less energy to evaporate the water to separate the contaminants therefrom. This process is particularly desirable in view of rising energy costs.
Alternative desalinization methods may include membrane-based processes such as reverse osmosis (RO), electrodialisys reversal (EDR), nanofiltration (NF), forward osmosis (FO) and membrane distillation (MD). Of these desalinization processes, reverse osmosis is the most widely used. Reverse osmosis uses semi-permeable membranes and pressure to separate salt and other impurities from water. Reverse osmosis membranes are considered selective. That is, the membrane is highly permeable to water molecules while highly impermeable to salt and other contaminants dissolved therein. The membranes themselves are stored in expensive and highly pressurized containers. The containers arrange the membranes to maximize surface area and salt water flow rate therethrough. Conventional-osmosis desalinization systems typically use one of two techniques for developing high pressure within the system: (1) high-pressure pumps; or (2) centrifuges. A high-pressure pump helps filter salt water through the membrane. The pressure in the system varies according to the pump settings and osmotic pressure of the salt water. Osmotic pressure depends on the temperature of the solution and the concentration of salt dissolved therein. Alternatively, centrifuges are typically more efficient, but are more difficult to implement. The centrifuge spins the solution at high rates to separate materials of varying densities within the solution. In combination with a membrane, suspended salts and other contaminants are subject to constant radial acceleration along the length of the membrane. One common problem with reverse osmosis in general is the removal of suspended salt and clogging of the membrane over time.
Operating expenses of reverse osmosis water desalinization plants are primarily determined by the energy costs required to drive the high-pressure pump or centrifuge. A hydraulic energy recovery system may be integrated into the reverse osmosis system to combat rising energy costs associated with already energy intensive processes. This involves recovering part of the input energy. For example, turbines are particularly capable of recovering energy in systems that require high operating pressures and large volumes of salt water. The turbine recovers energy during a hydraulic pressure drop. Thus, energy is recovered in a reverse osmosis system based on pressure differentials between opposite sides of the membrane. The pressure on the salt water side is much higher than the pressure on the desalinated water side. The pressure drop produces considerable hydraulic energy recoverable by the turbine. Thus, the energy produced between high pressure and low pressure sections of the reverse osmosis membrane is harnessed and not completely wasted. Recovered energy may be used to drive any of the system components, including the high-pressure pump or centrifuge. Turbines help reduce overall energy expenditures to perform desalinization.
In general, reverse osmosis systems typically consume less energy than thermal distillation and is, therefore, more cost effective. While reverse osmosis works well with somewhat brackish water solutions, reverse osmosis may become overloaded and inefficient when used with heavily salted solutions, such as ocean salt water. Other, less efficient desalinization methods may include ionic exchange, freezing, geothermal desalinization, solar humidification (HDH or MEH), methane hydrate crystallization, high-grade water recycling or RF induced hyperthermia. Regardless of the process, desalinization remains energy intensive. Future costs and economic feasibility continue to depend on both the price of desalinization technology and the costs of the energy needed to operate the system.
In another alternative method of desalinization, U.S. Pat. No. 4,891,140 to Burke, Jr. discloses a method of separating and removing dissolved minerals and organic material from water by destructive distillation. Here, water is heated to a vapor under controlled pressure. Dissolved salt particles and other contaminants fall out of the solution as water evaporates. An integrated hydrocyclone centrifuge speeds up the separation process. The heated, high pressure clean water transfers energy back to the system through heat exchange and a hydraulic motor. Net energy use is therefore relatively lower than the aforementioned processes. In fact, net energy use is essentially equivalent to pump loss and heat loss from equipment operation. One particular advantage of this design is that there are no membranes to replace. This process removes chemicals and other matter that would otherwise damage or destroy membrane-based desalinization devices.
Another patent, U.S. Pat. No. 4,287,026 to Wallace, discloses a method and apparatus for removing salt and other minerals in the form of dissolved solids from salt and other brackish waters to produce potable water. Water is forced through several desalinization stages at high temperature and at high centrifugal velocities. Preferably, the interior components spin the water at speeds up to Mach 2 to efficiently separate and suspend dissolved salt and other dissolved solids from the vaporized water. The suspended salt and other minerals are centrifugally forced outward to be discharged separately from the water vapor. The separated and purified vapor or steam is then condensed back to potable water. The system requires significantly less operational energy than reverse osmosis and similar filtration systems to efficiently and economically purify water. One drawback of this design is that the rotating shaft is built into a vertical chamber. As a result, the rotating shaft sections are only solidly anchored to the base unit by a bearing and a bearing cap. At high rotational speeds (e.g. over Mach 1), vibrations cause excessive bearing shaft and seal failure. Another drawback is that a series of chambers are bolted together in housing sections. The perforated plates are coupled to these sections by an O-ring seal. The housing and O-ring seals tend to wear over time due to salt penetration because the multiple chambers and housing sections are connected via a plurality of nuts and bolts. In particular, the assembly of the Wallace design is particularly laborious. Maintenance is equally labor intensive as it takes significant time to disassemble each of the housing sections, including the O-rings, nuts and bolts. Of course, the device must be reassembled after the requisite maintenance is performed. Each housing section must be carefully put back together to ensure proper sealing therebetween. The system is also prone to a variety of torque and maintenance problems as the device ages, such as O-ring leakage. Moreover, the rotating shaft is connected to the power source by a gear drive, which contributes to the aforementioned reliability problems associated with the bearings, shafts and seals. The system also fails to disclose a means for regulating the speed of the rotating shaft sections according to the osmotic pressure of the salt water being desalinated. The static operation of the Wallace desalinization machine is therefore not as efficient as other modern desalinization devices.
Thus, there is a need in the art for an improved system that includes sensors for monitoring real-time system information and controls for adjusting the mechanical operation of the system to maximize decontamination of the water, such as desalinization of the water, and minimize energy consumption. Such a system should further incorporate multiple recycling cycles to increase the recovery of potable water from approximately eighty percent to between approximately ninety-six percent to ninety-nine percent, should incorporate a polymer aided recovery system to extract trace elements of residue compounds and should consume less energy than other desalinization systems known in the art. The present invention fulfills these needs and provides further related advantages.